Fix NPE when favicon is updated.

chrome/android/java/src/org/chromium/chrome/browser/tab/Tab.java

Index: chrome/android/java/src/org/chromium/chrome/browser/tab/Tab.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/tab/Tab.java b/chrome/android/java/src/org/chromium/chrome/browser/tab/Tab.java
index 10097b49d5821b637c743ef0392ccfd368b8fab3..cbf51a80a1ec6dafc3e41ba90c97e955d1add508 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/tab/Tab.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/tab/Tab.java
@@ -2089,6 +2089,7 @@ public class Tab implements ViewGroup.OnHierarchyChangeListener,
 
     @CalledByNative
     protected void onFaviconAvailable(Bitmap icon) {
+        if (icon == null) return;
         String url = getUrl();
         boolean pageUrlChanged = !url.equals(mFaviconUrl);
         // This method will be called multiple times if the page has more than one favicon.